And today's question.

What is all this about then?

Aristotle

not the greatest scientist in the world if the truth be told

Why does this happen?

Because they WANT to be there.

Heavy things PLACE is the floor, light things PLACE is the air

So, naturally, heavy things will fall quicker than light ones.

Excellent. What's next?

Galileo Galilei (born 1564)

  

His father Vincenzo wrote:

 

“It appears to me that those who rely simply on the weight of authority to prove any assertion, without searching out the arguments to support it, act absurdly. I wish to question freely and to answer freely without any sort of adulation. That well becomes any who are sincere in the search for truth.”

Galileo decide to test Aristotle's idea.

so will we...

What do we mean by 'faster' anyway?

He discovered that the rate of change of speed was important, and he defined this as ACCELERATION.

So we have several very important concepts before Isaac Newton.

average speed

instantaneous speed

the rate of change of speed - acceleration

 

And a 'retarding force' which we now call:

FRICTION

 

Galileo's ramp experiment

in the year Galileo died, the man who would be buried here was born

Newton's 1st Law

Corpus omne perseverare in statu suo quiescendi vel movendi uniformiter in directum, nisi quatenus a viribus impressis cogitur statum illum mutare.

Every body persists in its state of being at rest or of moving uniformly straight forward, except insofar as it is compelled to change its state by force impressed

Newton's 2nd Law

Mutationem motus proportionalem esse vi motrici impressae, et fieri secundum lineam rectam qua vis illa imprimitur.

F = ma

Newton's 3rd Law

Actioni contrariam semper et æqualem esse reactionem: sive corporum duorum actiones in se mutuo semper esse æquales et in partes contrarias dirigi.

To every action there is always an equal and opposite reaction: or the forces of two bodies on each other are always equal and are directed in opposite directions.

Year 8 Force and Motion

By Gavin King

Year 8 Force and Motion

Aristotle, Galileo and Newton

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